Various hybrid powertrain architectures are known for managing the input and output torques of various prime-movers in hybrid vehicles, most commonly internal combustion engines and electric machines. Series hybrid architectures are generally characterized by an internal combustion engine driving an electric generator which in turn provides electrical power to an electric drivetrain and to a battery pack. The internal combustion engine in a series hybrid is not directly mechanically coupled to the drivetrain. The electric generator may also operate in a motoring mode to provide a starting function to the internal combustion engine, and the electric drivetrain may recapture vehicle braking energy by also operating in a generator mode to recharge the battery pack. Parallel hybrid architectures are generally characterized by an internal combustion engine and an electric motor which both have a direct mechanical coupling to the drivetrain. The drivetrain conventionally includes a shifting transmission to provide the preferable gear ratios for wide range operation.
One such parallel hybrid powertrain architecture comprises a two-mode, compound-split, electro-mechanical transmission which utilizes an input member for receiving power from a prime mover power source and an output member for delivering power from the transmission. First and second motor/generators are operatively connected to an energy storage device for interchanging electrical power between the storage device and the first and second motor/generators. A control unit is provided for regulating the electrical power interchange between the energy storage device and the first and second motor/generators. The control unit also regulates electrical power interchange between the first and second motor/generators.
Engineers implementing powertrain systems encounter driveline vibrations, which typically range from unnoticeable to objectionable to an operator. Driveline vibrations are customer dissatisfiers, and may reduce service life of one or more driveline components. Typically, engineers attempt to manage driveline vibrations by implementing systems which operate to cancel torque oscillations at one specific frequency, or over a range of frequencies, or a set of frequencies chosen based upon gear ratio at which the driveline is currently operating. Such torque cancellation systems typically pass driveline inputs through signal conditioning filters, which slow system responsiveness. Slow system response often leads to a bump or overshoot that occurs when there is an aggressive operator torque request, due to delays in transient responses required to develop filters. Such systems often use a single feedback variable, typically engine speed, and command a single control signal, typically engine torque. However, single feedback/single control vibration control systems do not provide adequate damping in a system having multiple devices operable to generate vibrations in a driveline.
A hybrid powertrain system is exemplary of a system having multiple devices operable to generate vibrations in a driveline, which therefore drives a need for an alternative method and apparatus to control driveline vibrations.
Therefore, there is a need for a method and apparatus to provide driveline damping for a hybrid powertrain control system over the operating range of the powertrain. There is a further need to provide driveability performance similar to that of a vehicle having a torque-converter in a vehicle equipped with a hybrid driveline, especially in a vehicle equipped with a hybrid driveline that incorporates manual transmission configurations such as direct connection between an engine, electric motors, and transmission input shafts.